Your pressure tester is really only useful on a stone cold engine. If you connect up the tester and start the engine, the expanding coolant will increase the pressure. Once you stop the engine, the coolant will begin to cool and the pressure will come down. Therefore, a loss of pressure on a cooling engine does not indicate a leak.

When you use the pressure tester, use it first thing in the morning and let it sit for awhile. It should not lose any pressure over an hour. If it does lose pressure, it may be for the following reasons:
1) external coolant leak. look for seepage at all hose connections, coolant elbows, heater core, radiator, throttle body, frost plugs, knock sensors, block heater.
2) internal coolant leak. Look for signs of coolant in the oil, white smoke in the exhaust on startup. IF THE PRESSURE DROP IS QUITE RAPID, DO NOT START THE CAR, YOU COULD HYDROLOCK THE ENGINE. If you have a rapid pressure drop and it's internal, pull the plugs and crank the engine. If you see coolant spewing out the plugs, it's the LIM or UIM.
3) bad seal on the pressure tester.

If small pressure loss, could be due to
4) air pockets
5) coolant hoses expanding.

I'm not sure about items 4 and 5. I had a small drop (1-2 psi over a few hours), but no signs of coolant loss. I have new hoses that are probably more flexible. As for air pockets, increasing the pressure will cause the air to dissolve into the water and lower the pressure.

 

What was your pressure loss on the cold engine? Could you find any external leaks?

Also, take an ohmmeter If it and probe the resistance of the LIM gasket. If it does not conduct electricity, it is the old style nylon carrier which is known to dissolve in Dexcool. If it conducts electricity, it has been replaced already and all you need to worry about is the UIM.

Internal leaks are usually the LIM gasket, UIM erosion around the EGR stovepipe. The LIM gasket should be replaced with the aluminum carrier gasket from GM, and the UIM should be replaced with the "Surefix" from APN.

 

whats a surefix APN? I have been going to Rock-Auto would they have it?

Thanks
Bob R

 

Thanks for the tips.
Yes on start-up I see white smoke out the exhaust. And eventually
the coolant reservoir empties. Sometimes the car is hard to start (like a bad starter motor or out of time engine) especially after it been running a while ,Hydrolock? on my 93 I replaced the UIM (with a Dorman) as well as upper and lower gaskets. I guess I need to do this again!
GM didn't learn this yet?? maybe on the next "bailout" EH!

thanks guys:icon_lol:
Bob R

 

Have you thought about whether or not you are going to go with Dex Cool when you refill?
If you do go with Dex Cool, then when refilling/bleeding the air out of the system I'd consider a method I found on the net that is supposed to ensure you get the coolant system bled of all air.
Even if you do not go with Dex Cool, I'd still consider this method to bleed the coolant system of air.

View topic - Coolant Fill Procedure for L36 (others similar) : PontiacBonnevilleClub.com

 

William,
was that Felpro gasket an aluminum framed gasket? I could never tell from the online descriptions and just went with GM aluminum framed ones myself.

Ribb55,

If you still have the plastic framed LIM gasket, make sure you do your LIM gasket as well.

 

Yup, that one is aluminum, the 2nd design GM one I think is mainly for those that want to add a little aftermarket power, so I've read.
I was not sure before I ordered it, till I googled the part number and found a good image of it.

 

was there a good 3800?

I have to wonder. In July I wrecked my 93' Olds 88. Left front fender hit (Geico totaled it, anybody need parts?) Anyway, went out and got a 97'
Lesabre w/a 3800 (of course) it seems the engine was redisigned, different intakes,different AC compressor, Sensors, on and on Nearly nothing can be used on the 97' from the 93'.
THe differences end there, because I just completed doing the Upper and Lower intakes, just like the 93' Some electrical problems' just like the 93'
and the tranny is acting "jerky" just like the 93'
My question is: at what year (if there is one) that the 3800 got reliable.
I hate to say it, I think I am done being a "GM guy" I prefer American cars
but Ford? Dont know, guess I am a little angry/disappointed

who knows maybe on the next "bailout" Gm might get it right


Bob R

 

As I understand it, the pre-Dexcool 3800 was quite reliable, especially the series I as far as I know. The Series II 3800 becomes pretty much as reliable as the Series I when the UIM is replaced with the Surefix intake and aluminum framed LIM gaskets.

The trouble with finding a reliable vehicle is that all makes/ models have issues, and, as far as I know, all makes/models have dropped in reliability in the last decade. My 92 Grand Marquis has 350000km on it. I did have the tranny rebuilt once, but I'm not convinced it needed a rebuild. I was sucked into having it redone. The only sign of trouble was a tranny leak from the torque converter area. The only other major work I had done was valve stem seals. Newer Grand Marquis have more issues including timing chain problems, some models have trouble with their plastic intake manifolds, and the list grows as models become more recent. 2000+ Lesabres have frequent window regulator failures (actually affects a wide range of GMs). Most GMs will have trouble with their LIM gaskets at one time in their lives. The series III 3800 went back to an aluminum intake (I believe), but I don't think it was ever available in the Lesabre or Park Avenue. I don't know too much about Honda or Toyota reliability, but you really pay a premium for those. If you can do your own repairs, you can save thousands. Newer vehicles with direct injection are having problems with intake valves because they no longer have fuel washing and cleaning the intake valves.